A French Rafale fighter jet takes on fuel March 19 during the initial French attacks on Libya. Subsequent attacks have targeted pro-Qaddafi ground forces, notably those near the de facto rebel capital of Benghazi.

Paris — The decision for the international community to take military action in Libya, sanctioning airstrikes to beat back Muammar Qaddafi's forces as they gained on rebel strongholds, has returned the idea of humanitarian intervention to the world stage. It's a notion that has lain dormant – and was discredited in many corners – after the Iraq war, but has now returned, championed by many of the same countries that were the greatest opponents of invading Baghdad.

The United Nations Security Council Resolution 1973, which approved using "all necessary means" short of a ground invasion to protect Libyan civilians, recalls many of the same humanitarian principles that led to intervention in Bosnia, Kosovo, and Rwanda, where the aim was to cross borders to prevent the further slaughter of innocent civilians.

Those ideals are back in play, though whether they will be popularly legitimized in Libya remains unclear. France seems certain they will. While it was the most ardent voice against the Iraq war, France has emerged as the champion of intervention in Libya after being slow to support revolutions in Tunisia and Egypt.

Still, many questions remain about the way forward. What's the international endgame? Is the real goal regime change? With NATO assuming control of the mission, how far will it go to support the rebels? Are the humanitarian arguments, enshrined in the 2005 UN principle of a "responsibility to protect," sometimes called R2P, practical in Libya? The uncertainties are large. But the principle involved represents a decades-long effort to consciously articulate the rights of people to life and liberty into the realm of international law.

Reaching consensus on intervention

The push for intervention, however, was not a dry application of principles. It was made feasible by a unique set of circumstances erupting across the Middle East that gave "idealists" the upper hand in the White House, on Downing Street, and at the Élysée Palace.

Policymakers feared the "Arab spring" and its homegrown and secular impulses would be crushed in Libya by Mr. Qaddafi's forces bearing down on Benghazi, the unofficial capital of the rebel movement. The invitation of the Arab League for a no-fly zone gave crucial cover for military action, which could have been interpreted in the Arab world as Western imperialism. And the French and British, with relatively sudden and strong support for Libyan rebels, pushed a reluctant President Obama to intervene at the 11th hour.

That idealism witnessed in recent months in Tunisia, Egypt, Bahrain, Yemen, Syria, and elsewhere in the Middle East helped foreign-policy idealists triumph over "realists" who resisted the idea of involvement in Libya as possibly entangling the West in another Mideast war.

"The Arab spring was at the core of this," says Charles Kupchan of the Council on Foreign Relations in Washington. "Those people supporting intervention are thinking more broadly than Libya. They are returning to a more idealistic foreign policy after two years of realism."

The European promise to lead on Libya also seemed to help force the American hand. As pressure grew on the United States to take action, Defense Secretary Robert Gates said it wasn't a question of whether the US could enforce a no-fly zone, "The question is whether it's a wise thing to do, and that's the discussion that's going on at a political level."

"The Americans have been saying to Europe all along, 'Where are our partners?' So when the Europeans and the French came to say, 'We want to be your partner,' that shifted things," says Mr. Kupchan.

On March 24, a week after the UN Security Council sanctioned military action in Libya, President Obama said, "It is in America's national interests to participate ... because no one has a bigger stake in making sure that there are basic rules of the road that are observed, that there is some semblance of order and justice, particularly in a volatile region that's going through great changes."

In Europe, too, it was all about the Arab push for democratic reform and an end to autocracy and Qaddafi's effort to snuff it out when the uprisings started in Libya.

"The main reason the Libya intervention is seen as legitimate is not a discovery that Qaddafi is a dictator," argues Jacques Rupnik, with the Center for International Studies and Research at Sciences Po in Paris. "The intervention is plausible to people in the Western democracies by its connection to the Arab spring and nonviolent movements for democratic change. Qaddafi was trying to roll that back, and Benghazi was seen as a tipping point."

Why this is different from Iraq

But the biggest hurdle, in Europe and elsewhere, to the Western-led airstrikes in the Arab world was the Iraq war, which supporters in 2003 described at the time as an invasion with a moral imperative.

Yet while "moral intervention" was used in the "Bush Doctrine" of preemption, the circumstances in Libya are different. The invasion of Iraq did not stem from a popular uprising on the Arab street. The Arab League opposed the Iraq war. The US road to Baghdad – a unilateral effort – did not stem from the imminent threat posed to (ostensibly) pro-democracy rebels. What's more, the Iraq ground invasion was followed by foreign occupation: Both ground invasion and foreign occupation have been ruled out by the terms of UN Resolution 1973.

"Only a fool would fail to acknowledge that the invasion of Iraq gave liberal interventionism a bad name," says Timothy Garton Ash, British historian and political writer. In stating a measured rationale for action in Libya, however, he argues that despite abuse of the concept, "a much more careful, law-abiding, and genuinely liberal version of it has quietly continued to develop. Building on the post-1945 tradition of human rights promotion and international humanitarian law, and working with and through the UN, this has brought us the International Criminal Court and the doctrine of a 'Responsibility to Protect,' also endorsed by the UN."

One of the leading voices in France in favor of intervention was Bernard-Henri Lévy. Mr. Lévy, who appeared on French TV as the Security Council voted March 17 on Resolution 1973, was asked what defines a "just" war.

"A war that wages war against war," said the philosopher. "The war of civilizations is over. Today, it is democracies versus dictatorships. That is what is at stake. In the case of Ben­ghazi, what is being played, at this very minute, is a race against time, a race between ... the battle of honor and courage at the Security Council, and ... the battle of terror, of the horror that Qaddafi arouses when he says he will take over the city."

It's in comments like those that similarities between Bosnia and Libya arise. "There's a clear connection between Bosnia intervention and the Arab world," argues Mr. Rupnik of Sciences Po. "The ideas still apply ... the missing link was Iraq, where neocons hijacked it for their own purposes. But the idea that we should not allow dictators to annihilate their populations has not been forgotten. You will not get a UN vote against large countries, China, Russia, the US. Conditions have to be right. But because you can't do everything everyplace, does not mean you should do nothing anywhere."

The actual military operation in Libya goes further than the Bosnian no-fly zone, which had little practical effect, but is not as robust as the Kosovo NATO intervention in 1999.

Criticism of strikes, Sarkozy

While Libyan intervention has many supporters, it has many critics, too. Ger­many and Russia oppose the operation. And there is great concern from many quarters that the international community acted too fast and without a clear plan.

Richard Falk, the Albert G. Milbank professor emeritus of international law at Princeton University, says the Libyan opposition was "violent from the start, and was more in the nature of a traditional insurrection against the established order than a popular revolution inspired by democratic values."

Despite Qaddafi's unquestionably hein­ous rule, "Does it validate a UN-authorized military intervention carried out by a revived partnership of those old colonial partners, France and Britain, and their postcolonial American imperial overseer? I think not," he says.

For France, there's also a definite political dimension to Sarkozy's role – he has no history of humanitarian intervention. Taking a lead role on Libya would seem to help France from being sidelined in Europe by a rising Germany. And his venture to help Libyan rebels could help restore French pride, stung by lingering French support for Egyptian and Tunisian autocrats after the start of the Arab revolutions, and boost his poll numbers, which have been at record lows.

Whatever the reason, says Arthur Goldhammer, at the Center for European Studies at Harvard University, Sarkozy "has stuck his neck out quite far in pushing for Western intervention in Libya, and he is now committed to see the mission through, though it may well strain French military capabilities to the breaking point."